The invention relates to a valve arrangement for an exhaust gas recirculation device of an internal-combustion engine with at least one inlet and at least one outlet, having an inlet on the internal-combustion engine outlet side, an outlet on the internal-combustion engine inlet side, and several, particularly two, flow paths extending between the inlet and the outlet and being parallel at least in areas. The valve arrangement has a first control element and a second control element for automatically regulating/controlling the fluid flow flowing between the inlet and the outlet and automatically regulating/controlling the distribution of this fluid flow between the several flow paths.
The exhaust gas recirculation (AGR) is a measure for reducing nitrogen oxide (NOx) particularly in the case of internal-combustion engines and is significant mainly in the case of lean-operation internal-combustion engines. In this case, a partial exhaust gas flow will be admixed again in an automatically regulated/controlled manner to the internal-combustion engine on the intake side by way of a flow duct via an exhaust gas recirculation valve.
The admixing of fuel gas can take place in front of or into the combustion chamber. The resulting mixture of fuel gas and exhaust gas has a lower useful heat value relative to the volume and therefore no longer reaches the temperature in the combustion chamber of the internal-combustion engine that is required for the formation of NOx. The exhaust gas recirculation normally takes place in the partial load range.
An improved NOx reduction can be achieved when the exhaust gas is cooled before the admixing to the fuel gas. This cooling takes place particularly in the case of higher-power engines, in which case an exhaust gas recirculation cooler is used. Further advantages are achieved when not only the recirculated exhaust gas flow as a whole but also its cooling can be automatically regulated/controlled.
From German patent document DE 10 2006 000 348 A1, an arrangement for the recirculation of exhaust gas is known which has an inlet on the side of the internal-combustion engine outlet, an outlet on the side of the internal-combustion engine inlet, and two parallel flow paths extending between the inlet and the outlet. One flow path includes an exhaust gas recirculation cooler, while the other flow path forms a bypass for bypassing the exhaust gas recirculation cooler. For automatically regulating/controlling the entire exhaust gas flow flowing between the inlet and the outlet, an exhaust gas recirculation valve is provided; an automatic regulating/controlling of the distribution of the recirculated exhaust gas between the two flow paths and thus of the cooling takes place by way of a cooling valve.
In this case, it is a disadvantage that, in addition to the two valve control elements, also the corresponding periphery, in particular including actuators, additional outputs at an internal-combustion engine control unit, cable harness taps, is required.
It is therefore an object of the invention to provide a valve arrangement of the concerned type, in which particularly an additional actuator, additional outputs on an internal-combustion engine control unit, and cable harness taps, can be eliminated. Such an arrangement should require only little space and be distinguished by a good tightness of the control elements in the closed condition and by high flow rates when the control elements are maximally opened.
This object is achieved by a valve arrangement for an exhaust gas recirculation device of an internal-combustion engine including at least one inlet and at least one outlet, having an inlet on the internal-combustion engine outlet side, an outlet on the internal-combustion engine inlet side, and several, particularly two, flow paths extending between the inlet and the outlet and being parallel at least in areas. The valve arrangement has a first control element and a second control element for automatically regulating/controlling the fluid flow flowing between the inlet and the outlet and automatically regulating/controlling the distribution of this fluid flow between the several flow paths. According to the invention, a common actuator is provided for actuating the first control element as well as the second control element.
The actuator can preferably be adjusted between a first actuator end position and a second actuator end position. An actuator starting position is provided which is situated between the first and the second actuator end position, particularly at least approximately in the center between the first actuator end position and the second actuator end position. In this case, starting from the actuator starting position, an actuation is made possible in the direction of the first actuator end position and in the direction of the second actuator end position.
During an actuation starting from the actuator starting position in the direction of the first or the second actuator end position, it is particularly advantageous for the first control element and the second control element to be actuated successively and/or simultaneously. Here, an actuation of the first and of the second control element can take place in different fashions. Likewise, it is advantageous, during an actuation starting from the actuator starting position in the direction of the first actuator end position, to actuate only the first control element or only the second control element, and during an actuation in the direction of the second actuator end position, to actuate only the respectively other control element. Also, an actuation of only the first control element during an actuation starting from the actuator starting position in the direction of the first or the second actuator end position offers special advantages.
The first control element and/or the second control element are expediently acted upon by spring force in the closing direction, so that by way of the actuator an actuation takes place in the opening direction, and in the closing direction the first and/or the second control element follows the actuator in a manner acted-upon by spring force. By way of this arrangement, a fail-safe function is also ensured. Likewise, it is considered to be useful for the first control element and/or the second control element to be restrictedly guided in the opening and in the closing direction. In this case, the closing force does not depend on the force of a spring, but is also applied by the actuator and the corresponding control element follows the actuator not only in a force-locking but also in a form-locking manner.
According to a particularly preferred embodiment of the invention, a first transmission device is provided between the actuator and the first control element, and a second transmission device is provided between the actuator and the second control element. The transmission devices are used for converting the actuator movement into a movement of the control elements, and in each case permit transmission ratio profiles especially adapted to the requirements.
In the case of a valve arrangement in which the actuator is a rotary drive, preferably the first transmission device and/or the second transmission device is suitable for converting a rotatory movement to a linear movement.
It is very advantageous for the first transmission device and/or the second transmission device to have at least one gate and at least one driving device interacting with the latter. In this context, a “gate” is also an element driving a driving device, even though no or at least no significant relative movement takes place between the driving device and this element.
It was found to be particularly useful that, by way of the second transmission device, a discontinuous movement transmission is achieved between the actuator and the second control element, so that the second control element will not always be actuated when the actuator is operated.
It is also advantageous for the first transmission device and/or the second transmission device to have a toothing with an input and an output toothing.
According to a particularly preferred embodiment of the invention of the valve arrangement, the second control element is acted upon by spring force in a bistable manner in the direction of an opening or a closing position. The second control element is therefore acted upon by a force in the direction of the opening or closing position, in which case, for example, during actuation starting from the opening position, first an actuation takes place against the (decreasingly effective) spring force; then a neutral dead center is reached in which the spring force is not active in the opening or closing direction, and then, as a result of the spring force, a “snapping over” takes place in the direction of the closing position. In the reverse direction, the bistable control element will act correspondingly.
By means of the actuator and the second transmission device, the second control element can expediently be displaced in a dead-center-overriding manner between the opening position or a closing position.
The second transmission device preferably includes transmission elements having play and a force-type connection which changes as a function of the actuating direction, so that a hysteresis is achieved. When the dead center is exceeded, an actuation of the second control element is therefore obtained caused by the spring force while passing through the play, independently of an actuator movement. During an opening movement, a correlation of movements between the actuator and the control element exists that is different than during a closing movement.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.